1. Field of the Invention
The present invention relates to a mechanical sensor for detecting a mechanical property.
2. Description of the Prior Art
Recently, it is required for electronic devices and instruments to have a more compact and thinner size. At present a mechanical sensor which uses a stress-magnetic effect is available practically and it comprises an amorphous magnetic alloy ribbon adhered on a cylinder. The alloy has a positive saturation magnetostriction constant, and a change in magnetic permeability of the ribbon due to applied stress is detected with a solenoid coil (refer for example SAE TECHNICAL PAPER SERIES 920700).
However, the above-mentioned prior art sensor uses a coil made of a wire wound like a solenoid and a bulk magnetic layer. Therefore, it is difficult to reduce the size of a mechanical sensor or to integrate it in a device. Further, because the thickness of the magnetic layer is as large as 20-30 .mu.m and the diameter of the wire is as large as 20-30 .mu.m, it has an upper limit to be used at higher frequencies.
A strain gauge is used as a planar mechanical sensor. However, its sensitivity is as low as 10.sup.-3 of that of a sensor using of stress-magnetic effect.